In the manufacture of business forms, it is almost always necessary to seal one part of the form construction with respect to another. This is typically accomplished by utilizing an adhesive which acts between the two portions of the business form to be fixed together. Oftentimes heat activated adhesives are utilized, but in many circumstances it is desirable to utilize pressure sensitive adhesives.
A sealing system for business forms used with one type of pressure sealing adhesive requires that the adhesive applied to the forms during manufacture be capable of cohesive bonding to a fiber tearing strength when pressure sealed after computer printing by the end user, but must be entirely free of adhesive bonding under all conditions of normal handling during manufacture, storage and imaging. Thus the margins of pressure applied to the paper during normal handling, and the pressure applied to effect fiber tearing bonds are widely separated.
A typical pressure sealing piece of equipment for use with business forms uses a multiple roll sealing system to apply pressure to the entire web (or the entire individual sheets) being processed. Those rolls are capable of exceeding the threshold unit pressure required, which is quite high, typically about 200 lbs. per lineal inch of paper width when using a succession of two or three pressure couples. This requires a very rigid yet accurate mechanical system. While the application of such high forces requires massive and precise construction of the sealer, it is also necessary that the web or sheet manifold be clean--that is that there be no disturbances in the surface configuration. Therefore it is extremely difficult to utilize such equipment with inserts, window patching, folds internal to the form, etc., since such build ups in thickness or non-uniformities in the surface characteristics decrease the unit pressure at the sealing edges and could increase the sealing pressure in the inclusion area so that a jam or physical tearing of the sheet occurs. When inserts are provided, there also is the problems of "tenting" or "pillowing".
According to the present invention, a method and apparatus are provided that overcome the problems associated with full-width pressure sealing systems. According to the present invention it is possible to continuously, and at high speed, act upon business forms including those having inserts, window patching, folds internal to the forms, and other surface non-uniformities. The "pillowing" effects (where the sealed manifold is forced apart), and the "tenting" effects (where various plies of the assembly shift relative to each other and thereby prevent formation of a completely flat form) are substantially avoided.
The general manner in which the desirable results are accomplished according to the invention is by effecting sealing along only the pressure sensitive adhesive strips of the business forms--rather than along the entire surface of the forms. This allows the coupling force between each sealing roll pair to be reduced from about 1,000 lbs. in the prior art, to about 100-200 lbs., dependent on the ratio of total form width to sealing bond width. This also allows production of a system that is much less massive than conventional, and one that is reliable and simple and easy to utilize.
According to one aspect of the present invention, a method of handling business forms is provided, each form having at least one strip of pressure sensitive adhesive of a predetermined width for affixing one part of the form to another part. The method comprises the step of (a) automatically, in a continuous, sequential manner, acting on successive individual business forms to apply a force to them sufficient to activate the pressure sensitive adhesive to fix one part of the form to another, the force being applied only to the approximate area of the predetermined width of adhesive. Typically the business forms would each have first and second generally parallel strips of pressure sensitive adhesive each of a predetermined width, and step (a) would be practiced so as to apply the activating force to the approximate areas of both strips of adhesive. The business form may have a third (or others) strip of pressure sensitive adhesive generally perpendicular to the first strip, and of a predetermined width. In a continuous and sequential manner, according to the method of the invention the form would be acted on to apply a force to the third strip, too, this force also being applied only to the approximate area of the predetermined width of the third adhesive strip. Prior to the practice of step (a), the business form may be initially configured by folding a sheet of paper to provide at least two plies. The paper may be V-folded, C-folded, or Z-folded. An insert may be inserted between the plies, in which case the adhesive activating step or steps are practiced so that activating force is not applied to any area of the business form containing the insert.
According to another aspect of the invention a pressure applying system for applying pressure to business forms to activate pressure sensitive adhesive associated with the forms is provided. The system comprises a frame, and a pressure applying device operatively connected to the frame. The pressure applying device comprising means for simultaneously applying pressure along a pair of spaced, generally parallel strips while simultaneously conveying business forms through the device, including two sets of narrow width upper and lower rollers. The upper roller of each set is disposed above and in peripheral engagement with the lower roller of that set along a common vertical center line. The pressure applying device also preferably further comprises a pair of conveyor transport belts or tapes, one associated with each set of rollers, and mounted interiorly of the rollers for assisting conveyance of business forms between the rollers. Each upper and lower roller preferably has a segment with an elastomeric material periphery to assist accurate rotary displacement of said upper and lower roller pairs.
According to a further aspect of the present invention, there is provided a first pressure sealing device comprising upper and lower rollers disposed on a common vertical centerline, and means for applying a force to the upper roller sufficient to effect activation of the pressure sensitive adhesive of the business forms acted thereon, the rollers having a width approximately equal to the predetermined width of a strip of pressure sensitive adhesive which they act upon (e.g. about 0.3-0.7 inches). A second pressure sealing device, substantially identical to the first device, is also provided. Feeding means feed business forms in a continuous manner to the first device upon exiting the first sealing mechanism. A 90.degree. transfer conveyor means continuously feeds business forms from the first device to a second similar sealing device; and, discharge conveyor means convey sealed forms away from the second device.
According to yet another aspect of the present invention a pressure applying distinct module is provided. The module comprises: A stationary frame, a lower roller, a first shaft for mounting the lower roller for rotation about a first generally horizontal axis, the axis being fixed with respect to the frame, and an upper roller. Also provided are: means for mounting the upper roller so that it is distinct from the first shaft and frame, but so that the upper and lower rollers are on a common vertical center line, and so that it is rotatable about a second generally horizontal axis, parallel to the first axis; and force applying means for applying a force between the frame and the upper roller so that the periphery of the upper roller is operatively pressed into engagement with the periphery of the lower roller. The first shaft is rotated about its axis of rotation by a motor.
The force applying means (e.g spring or hydraulic) preferably applies sufficient force to the upper roller so that there is a pressure of about 100-200 lbs per lineal inch exerted by the rollers on the sheet material therebetween.
The rollers and the apparatus according to the invention typically are steel pressure wheel couples having a diameter of about three inches, and separated by a linear distance of about 31/2 inches. They have an operative peripheral width of about 0.3-0.7 inches (e.g. about 1/2 inch) so that they act only on that portion of the business form on which the strip of pressure sensitive adhesive is applied. Preferably horizontally spaced sets of rollers are provided so that multiple parallel strips of pressure sensitive adhesive can be acted upon at the same time, and the horizontal spacing between the rollers perpendicular to the direction of movement of the forms may be adjusted to accommodate forms of different dimensions. The second pair (in the direction of form movement) of rollers of each set is very slightly larger in diameter than the first, to provide a slight tension on the forms during conveyance.
It is the primary object of the present invention to provide for the effective high speed automatic sealing of business forms in a continuous, successive manner by applying pressure only to strips of pressure sensitive adhesive associated with the forms, and not other parts of the form. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.